I advocate keeping the 6.5X gain - it comes in handy when using 1V (or less) sources and HDR recordings (Live music, Movies, some Video Games). Particularly if you are using the O2 with headphones in the 90 dB efficiency range. If you think that will NEVER be the case, unity and 2.5x will probably be great.

Remember that if you wanted, you can use the windows volume control (for example), you get your levels where you want them with whatever phones you are using. Also, you can take the O2 from 2.5X to 6.5X to 1X, 2.5X if you want, but you can't "add" gain later!

Hmm, I am getting the ODAC+O2 combo so my source will always be the same. Either that or I'm misunderstanding you. :P

What compatible op amp chips do you recommend? What audible difference would it make?

im not sure how advantageous opamp rolling would be... the whole circuit was built around these specific ones, and the measured performance has been proved and tested to many times... just my 2 cents...

im not sure how advantageous opamp rolling would be... the whole circuit was built around these specific ones, and the measured performance has been proved and tested to many times... just my 2 cents..

agree with you in some points ..... but may be you want to alter the sound signature .... would want more bass presence ... warmer sound ,,, or more intimate sound ....opamps offers that kind of tweaking ... it is not something like a day and night difference but it is noticeable .... and even the same opamp sound different from implementation to another

im not sure how advantageous opamp rolling would be... the whole circuit was built around these specific ones, and the measured performance has been proved and tested to many times... just my 2 cents...

I agree. But this may give me something to do. I first have to make sure my relatively new O2 is fully functional before attempting any modifications. But then again, the O2 sounds great the way it is now.

agree with you in some points ..... but may be you want to alter the sound signature .... would want more bass presence ... warmer sound ,,, or more intimate sound ....opamps offers that kind of tweaking ... it is not something like a day and night difference but it is noticeable .... and even the same opamp sound different from implementation to another

Quote:

Originally Posted by r010159

I agree. But this may give me something to do. I first have to make sure my relatively new O2 is fully functional before attempting any modifications. But then again, the O2 sounds great the way it is now.

rolling opamps, or tubes for that matter, or whatever other hardware modifications, will ofcourse effect the sound and may well be part of a hobby, granted, no argument. if thats what you wanna do - go for it. im just saying, that of all the amps to mess around with, i find the choice of the O2 to be strange. its built to be a high performance, cheap alternative to otherwise way more expensive gear. the whole argument around it is whether or not it could actually achieve "perfect linearity", or "perfect neutrality" if you will. many people will tell you that it does, and as you can see, im not the only one raising my eyebrows, its just a little strange is all... after all the fuss and argument, its become somewhat of a "cult" product, and most of its buyers want that "neutral" response its so famous for...

all that being said - do whatever you want mate, i was just throwing in an opinion

If you love how the stock O2 sounds, then there is no real reason to swap op-amps.

I actually only did it because I don't love how it sounds with the Q701 and some brighter headphones.In this case I don't care about having the best measurements. I only care about what my ears tell me. Some minor coloration is OK.

I also found myself almost never using the O2 and op-amps (in most cases) are dirt cheap!

Swapping op-amps on the O2 is easy and all it requires is a few minutes. You don't even need to buy a chip puller. You can use a toothpick(!) or some pliers (not suggested).

So far i've tried the OPA2227 and LM4562. OPA2227 is nice, but seems better for the Q701 than HD-650. It seems to be a little warmer than the stock op-amps.

The LM4562 is a no go with the stock Q701, but I love it with the modded Q701 (which is warmer/bassier). Most say it's a brighter op-amp.

The differences are minor really. For something like a DT-990 or grado SR-325i swapping to the OPA2227 or OPA1234 might be a good idea.

I think you'll probably void your warranty though.

BTW I think the stock O2 is great with warmer headphones like my HD-650 and DJ100. With my O2, the HD-650 sounds exactly how it should without much change at all.

Haha, if you're nuts you could try getting the OPA627 to work with the O2. I don't think it's possible. I think that must be one of the most expensive op-amp there is. It's only single channel and you'd probably need one of those adapters. I don't even know if those fit on the O2. $34 for a single channel op-amp chip!!

The OPA2134s are just $4.50 each.

One i'd like to try is the AD8397. Not sure if it'd work and it'd require soldering onto an adapter.

Thanks for the comment, yes it takes a while to get used to if your used to a warmer source.

Look out in February for more from me on JDS labs products, including the ODAC

Do you feel like brighter headphones at the top like the HP100s and the DT 990 pros(250ohms) would sound unkind with this pairing of the ODAC and the O2, and, have you ever tried the CDAC+(ODAC better isolation and power supply)